Pickens gained notoriety and celebrity in the 1980s as a dealmaker who launched leveraged buyouts of oil companies including Phillips Petroleum Co, Gulf Oil Corp and Unocal Corp. Even though many did not succeed, he and his investors made substantial money from the sale of stock of his target companies.REUTERS | January 13, 2018, 13:28 IST

Pickens, 89 years old, said in a letter posted online that he plans to focus on his health and on entrepreneurship, philanthropic and political activities. He is still recovering from a serious fall last summer and suffered a series of strokes in late 2016.

"Trading oil is not as intriguing to me as it once was," he wrote in the letter posted on Friday. "It's no secret the past year has not been good to me, from a health perspective or a financial one."

The fund, which he formed in 1996, has struggled and in recent years its assets have been well below a peak of $2 billion in 2007, a spokesman said.

Pickens gained notoriety and celebrity in the 1980s as a dealmaker who launched leveraged buyouts of oil companies including Phillips Petroleum Co, Gulf Oil Corp and Unocal Corp. Even though many did not succeed, he and his investors made substantial money from the sale of stock of his target companies.

In 1956, he founded an oil production company that became Mesa Petroleum and ran it for nearly 40 years.

A decade ago, he unveiled his "Pickens Plan," a lobbying effort to wean the United States from OPEC oil by championing the use of alternative energy and natural gas. He spent in excess of $100 million to promote the effort, a spokesman said.

Brian Bradshaw and David Meaney, executives of the shuttered Pickens hedge fund, BP Capital, have started their own hedge fund, Assert Capital Management LP.

Their energy commodities fund will start operations next week with about $25 million, mostly from past investors. It plans to raise another $200 million this summer, Meaney said in an interview.

Pickens remains involved in his charitable foundation and on the board of Clean Energy Fuels Corp, which operates natural gas refueling stations.